Method and apparatus for simultaneously heating a plurality of fluids



Dec. 21, 1954 c. Buss METHOD AND APPARATUS FOR sIMuLTANEoUsLY HEATING A PLURALITY 0F F'LUIDS Filed Aprll 4, 1952 mrm..

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MY C United States Patent METHOD AND APPARATUS FOR SIMULTANE- OUSLY HEATING A PLURALITY F FLUIDS Charles Bliss, Ardsley, N. Y., assignor to Foster Wheeler gororation, New York, N. Y., a corporation of New Application April 4, 1952, Serial No. 280,675

8 Claims. (Cl. 196-116) This invention relates to heating and more particularly opparatus for simultaneously heating a plurality of The present invention provides a method of and apparatus for heating a plurality of different iiuids by gases of combustion of the same heater, wherein the proportion of heat from said gases transferred to each fluid is controlled.

The present invention further provides apparatus wherein one fluid is heated and vapor is generated from another uid in the same heater and wherein the amount of Vapor generated and the amount of heat absorbed by the firstmentioned fluid are independently controlled. The present invention may be used, e. g., in rthe refining of hydrocarbon oils wherein it is necessary to impart to the oils suiicient heat to effect their fractionation or conversion and also to supply steam for various steps of fractionation of the hydrocarbon oils, i. e., to operate a distillation unit or to revaporize some of the fractions before passing them through other fractionating apparatus for separation into further fractions. Normally, the temperature to which the oil is heated must remain constant, while the requirement for steam will vary. With the present invention oil is heated and steam is generated in the ksame heater, while the amount of steam generated and the amount of heat absorbed by the oil are independently controlled by interchanging surpluses or deficiencies inheat pick-up of the oil through controlling the passage thereof in heat exchange relationship with water, thereby generating steam independently of the heater to control the temperature at which the oil enters said heater and the amount of steam generated.

The invention will be understood from the following description when considered in connection with the accompanying drawing in which the single ligure illustrates diagrammatically apparatus of the invention in one ernbodiment thereof.

Referring to the drawing, reference numeral 10 designates a heater having a setting including vertical side walls 11 and 12, sloping side walls 13 and 14, opposite end walls-one of which is shown at 15, a roof 16 and a bottom 17. Suitable framework designated generally at 18 supports the walls and roof of the setting. The walls of the setting enclose a furnace 19 which is fired, as shown, by two fuel burners 20 and 21 located in the lower central portion of end wall 15.

The side walls and roof are lined with Huid conducting tubular members through which oil flows, as will hereinafter be fully described, which tubular members are heated principally by radiation from the production of combustion gases produced by burners 20 and 21. Vertical side walls 11 and 12 have horizontally extending tubular members 22 and Z3 respectively, While the sloping side walls 13 and 14 have similar tubular members 24 and 25 lining said walls respectively. Tubular members 26 line the portion of the roof 16 to the left of the center thereof. while tubular members 27 line the portion of roof 16 to the right of said center.

The heater has two convection tube bank sections 28 and 29 above bottom 17, each section comprising a plurality of horizontally extending tubes, section 28 being located approximately midway of side wall 11 and the vertical center line of the furnace, and section 29 being approximately midway of' side wall 12 and said center line. A bathe 3@ is supported above the sections 23 and 29 and extends the length of the furnace, but the opposite l sides of the bathe are spaced from the side walls' of the furnace sufficiently to provide elongated furnace gas passages 31 and 32 through which gases flow from the upper part of the furnace over the tubes of sections 28 and 29 respectively and into gas outlet passage 33 which discharges the gases at one end of the heater.

As shown, oil to be heated in the heater passes into sections 28 and 29 through inlet conduits 34 and 35 respectively which conduits receive said oil through an inlet line 36. From tube bank 28 oil flows through an outlet conduit 37 into tubes 22 lining wall 11, which tubes are serially connected with each other and with tubes 24 lining inclined wall 13, tubes 24 being also serially connected and in communication with roof tubes 26, also `serially connected. Oil flows from tubes 26 into an outlet connection 38 whence it passes into heated oil outlet line 39. Oil from section 29 ows therefrom through a line 40 into tubes 23 lining wall 12. Tubular members 23, 25 and 27 are serially connected with one another so that oil passes serially therethrough. From roof tubular members 27 oil Hows into an outlet line 41 which communicates with heated oil outlet line 39.

Tubular members 22, 23, 24, 25, 26 and 27 are screened by water wall tubes 42 spaced inwardly from said tubular members between said tubes and burners 20 and 21. Tubes 42 are positioned adjacent the spaces between tubular members 22, 23, 24, 25, 26 and 27 so that each tube 42 shades the tubular members on oppositeksides of said tube from gases of combustion from the burners. The lowermost tube 4-2 adjacent tubular members 22 receives feed water from feed water inlet line 43 through branch line 44, while lowermost tube 42 adjacent tubular members 23 receives water directly from line 43. Tubes 42 are serially connected and a steam off-take line 45 communicates with said tubes at the center of the row thereof adjacent roof tubes 26 and 27.

Heated oil, e. g., oil from a fractionating tower, which is to be further heated in heater 10 ows from a line 46 either into a heat exchanger 47 through line 48 and thence into inlet line 36 through connection 49, or into inlet line 36 through bypass 50, which bypass communi- Cates with lines 46 and 36 at the opposite ends thereof. Bypass 50 is controlled by bypass valve 51, which-bypass valve is operated by a temperature controller 52 which is responsive to the temperature in oil outlet line 39.

Oil flowing through tubular members 47 in heat exchanger 47 passes in heat exchange relationship with water pumped by a circulating pump`53 from water line 54 into said heat exchanger through a line 55. Passage of water through line 55 is controlled by a pressure-actuated valve 56. Steam generated in heat exchanger 47 flows through steam line 57 into steam space 58 in a steam and water drum 59. Steam off-take line 45 and line 57 are in communication so that the steam from both heater 16 and heat exchanger 47 is conducted into steam space 58 of drum 59. Water from water space 60 of drum 59 is pumped by a circulating pump 61 from space 60 through line 62 and thence into feed water inlet line 43. A level controller 63 is associated with drum 59 and is responsive to the pressure in the drum. Controller 63 communicates with the drum through a lower connection 64 and an upper connection 65, and communicates with pressurecontrolled valve 56 in line 55 so as to actuate said valve in response to the pressure in the drum to control the amount of water flowing into heat exchanger 47 through line 55 and thence into drum 59 through line 57.

Burners 20 and 21 receive fuel gas through fuel feed line 66 having feed Valve 67 therein. which valve 67 is controlled by a pressure controller 68 which communicates with steam space 58 of drum 59 through steam line 69 and with valve 67 through line 70 so that the flow of fuel to burners 20 and 21 is controlled in response to the pressure in drum 59.

In operation, water is passed into drum 59 through water line 54, circulating pump 53. heat exchanger 47 and line 57. Until the water reaches a predetermined level in drum 59, valve 56 in line 55 remains in a fully opened position, but when a predetermined level -is reached, level controller 63 operates valve 56 toward a closed position to decrease the ow of water into the drum. Throughout the operation of the apparatus of the Ipresent invention, level controller 63 actuates valve 56 in response to pressure in the drum so as to maintain the water in drum 59 at a predetermined level. Water is withdrawn from water space 60 of drum 59 through line 62 by circulating pump 61 and is passed by said pump into tubes 42 in heater 10 through feed water inlet line 43 and through branch line 44. In this manner, water for the generation of steam is supplied to tubes 42. Steam is withdrawn from tubes 42 through steam off-take line 45 and ows into steam space 58 of drum 59 through steam line 57. Steam from steam space 58 is rerinove7d1 from the drum through saturated steam conuit Oil to be heated in heater 10 is withdrawn from a fractionating tower or the like, not shown, which oil would normally be at approximately 460 F., and through lines 46 and 48 enters tube ow path 47l in heat exchanger 47, said oil causing steam to be generated in the heat exchanger by passing in indirect heat exchange relationship with the feed water therein, the mixture of steam and water thereafter passing into steam space 58 of drum 59 through line 57. After passing through flow path 47' the oil, which has been cooled by flowing in heat exchange relationship with the water in the heat exchanger, passes into inlet line 36 through connection 49, thereafter to enter the tubes of section 28 through inlet conduit 34 and the tubes of section 29 through inlet conduit 35. From section 28 oil ows through outlet conduit 37 into tubular members 22, thence into tubular members 24 and 26 to enter heated oil outlet line 39 through outlet connection 38. Oil from section 29 flows into tubular members 23 through line 40, thence into tubular members 25 and 27 thereafter to ilow into heated oil outlet line 39 through outlet line 41.

Tubular members 22, 23, 24, 25, 26 and 27 and tubes 42 are radiantly heated by gases of combustion in furnace 19, which gases pass downwardly through gas passages 31 and 32 and to gas outlet passage 33 after flowing in convection heat exchange relationship with the tubular members of sections 28 and 29.

In the above described operation the apparatus provides steam to ll a normal demand and provides a normally required amount of oil at a predetermined normal temperature.

With the apparatus of the present invention, should the demand for steam increase above the normal demand and the heated oil demand as to quantity and temperature remain constant, the level of water in steam drum 59 will be lowered below its normal level, causing level controller 63 to act on valve 56 in line 55 so that valve 56 will move toward an open position, thereby permitting the level of water to rise in said drum to said predetermlned level. The flow of an increased amount of water through heat exchanger 47 will cause oil flowing into flow path 47 from lines 46 and 48 to decrease in temperature so that oil entering heater 10 through oil inlet line 36 is at a lowered temperature. A decrease in pressure 1n steam drum 59 caused by increased steam demand w1ll 1n turn cause pressure controller 68 to actuate feed valve 67 in fuel line 66 to increase the amount of fuel flowing to burners and 21. This increase of the tiring rate of the burners will cause more steam to be generated in tubes 42, thereby increasing the steam pressure in drum 59 to said predetermined amount. The temperature of the oil passing through the tubular members 1n heater 10 is raised by the increased tiring rate of the burners.

Should the steam requirement be reduced below the n ormal requlrement and the heated oil demand as to quantlty and temperature remain constant, the pressure in steam drum 59 would tend to rise, which rise in pressure would cause pressure controller 68 to actuate feed valve 67 toward a closed position and decrease the ow of fuel 1n feed line 66 to burners 20 and 21. A reduction in the rlng rate of the burners will cause less steam to be generated and result in a decrease in the heat pick-up in the tubular members through which oil flows through heater 10. Temperature of the oil in oil outlet line 39 decreases. So that this temperature will remain constant even though the steam requirement is reduced, temperature controller 52 acts on bypass valve 51 so as to permit the ow of oil through bypass 50 and around heat exchanger 47. Bypassing of the oil around heat exc hanger 47 permits said oil to enter heater 10 through l 1ne 36 at a higher temperature. Decrease in the pressure m drum 59 because of decreased steam demand would cause valve 56 to be moved toward a closed position by action of level controller 63, decreasing the ow of water into heat exchanger 47 and drum 59 so that the Water level therein will be maintained at said predetermined level. While bypassing the oil around heat exchanger 47 decreases the total amount of steam generated, the decrease will be smaller compared to the amount of steam generated in heater 10 so that the pressure in drum 59 will not be suiciently affected to cause the tiring rate of burners 20 and 21 to be changed by pressure controller 68.

Should the heated oil load increase above normal requirements while the steam demand remains constant, the oil outlet temperature in line 39 will tend to fall, causing temperature controller 52 to open bypass valve 51 and permitting oil to bypass heat exchanger 47; less steam will be generated since heat exchanger 47 will not now operate for the generation of steam. Generation of less steam will cause the pressure in drum 59 to drop, thereby causing valve 67 to move toward an open position and thus increase the tiring rate of burners 20 and 21. Increased tiring of burners 20 and 21 will cause increased heating of the oil flowing through the tubular members in heater 10, thereby increasing the outlet temperature of the oil in oil outlet line 39. The deficit in steam generation caused by bypassing heat exchanger 47 will be made up by the increased tiring of heater 10 as well as by increasing the heating of the oil flowing through the tubular members in the heater.

Should the heated oil load decrease below normal requirements with the steam load remaining constant, the temperature of the oil in line 39 would tend to rise, causing temperature controller 52 to move valve 51 toward a closed position and causing oil to flow through heat exchanger 47. Temperature of the oil entering heater 10 would thereby be decreased. The pressure of the steam, however, would be increased, which would cause valve 56 to move toward an open position, the ow of water to heat exchanger 47 to increase, and controller 68 to decrease the flow of fuel to burners 20 and 21.

Inasmuch as changes may be made in the form, location and relative arrangement of the several parts of the invention and in the sequence of the various method steps without departing from the principles of the invention, it will be understood that the invention is not to be limited excepting by the scope of the appended claims.

What is claimed is:

l. Vapor generating and fluid heating apparatus comprising a setting having a furnace therein, burner means for producing a stream of products of combustion in the furnace, fluid conducting tubular members in the setting formingl a fluid ow path for uid to be heated, said flow path having an inlet for fluid to be heated and an outlet for heated Huid, said fluid conducting tubular members being disposed in the setting in heat exchange relationship with said stream of products of combustion, vapor generating surface so positioned in the furnace that said products of combustion flow in heat exchange relationship therewith prior to flowing in heat exchange relationship with said fluid conducting tubular members, said vapor generating surface having a liquid inlet through which liquid is fed thereto and a vapor outlet through which a mixture of liquid and vapor flows therefrom, a vapor and liquid drum with a vapor space and a liquid space therein, the liquid space being in communication with the vapor generating surface inlet so that liquid is delivered thereto from the drum, the vapor space being in communication with the vapor outlet of the vapor generating surface to receive vapor therefrom, a saturated vapor outlet conduit in communication with the vapor space of the drum to receive saturated vapor therefrom, burner control means responsive to pressure in said drum and operatively associated with said burner means, said burner control means being operative by said pressure in the drum so as to increase the tiring rate of fuel to said burners when the pressure in the drum decreases and to decrease the ring rate of fuel to said burners when the pressure in the drum increases, a heat exchanger, uid conduit means communicating with said heat exchanger and through which heated fluid is conducted to the heat exchanger, feed liquid conduit means communieating with the heat exchanger and through which feed liquid to be heated is conducted to the heat exchanger, the heat exchanger being so constructed and arranged that said heated uid and feed liquid pass in indirectheat facetas? exchange relationship with .one another, Vsaid feed liquid thereby becoming heated :and said duid becoming cooled, feed liquid .control means located to control ythe :dow of feed liquid to said heat exchanger, .the .feed liquid control means being operative .to increase or decrease the flow of feed liquid to .said heat exchanger, said feed liquid control means being operative in response to the Achange of liquid level in said drum so as to decrease the dow of feed liquid to the drum when the liquid level in the :drum exceeds a predetermined level and to increase the llow of feed liquid to the drum when the liquid 4level in the drum falls below said predetermined level, a cooled fuid outlet conduit in communication lwith the .heat exchanger to receive cooled fluid therefrom and with said iduid flow path inlet to deliver cooled iiuid thereto, a heated feed liquid conduit in communication with the heat exchanger to receive heated feed liquid `-therefrom and with said vapor and liquid drum to deliver heated feed liquid thereto, a bypass yconduit communicatmg `with :said fluid conduit and said fluid llow path .so :that 'ni'd from said uid conduit may be bypassed around said heat exchanger 'and into said fluid ow path, and :temperature responsive control means operatively associated vwith said bypass to control the flow of liuid through said bypass, said ternperature responsive control means being 'operative in .response to said temperature to increase or decrease the flow of uid through said bypass, the temperature control means being responsive to :the temperatures of said heated fluid so as to increase the flow of duid through the bypass and around the heat exchanger when the temperature of the heated fluid decreases and to decrease the flow of duid through the bypass .so as to increase the ow thereof through the heat exchanger when the temperature of said heated uid increases.

2. Vapor generating and duid heating apparatus comprising a setting having a furnace therein., burner means for producing a stream of products -of `combustion in the furnace, uid conducting tubular members in the vsetting forming a fluid ow path for tluid to be heated, `said flow path having an inlet for fluid to be heated and an outlet for heated fluid, .said fluid lconducting tubular members being disposed in the .setting in heat exchange relationship with said stream of products of combustion, vapor generating surface so positioned in the furnace that said products of combustion ow in heat exchange relationship therewith prior to ilowing in heat exchange relationship with said fluid conducting tubular members, said vapor generating surface having a liquid inlet through which liquid is fed thereto and a vapor outlet through which a mixture of liquid and vapor flows therefrom, a

vapor and liquid drum with a vapor space and a liquid space therein, the liquid space being in communication with the vapor generating surface inlet so that liquid is delivered thereto from the drum, the vapor space being in communication with the vapor outlet of the vapor generating surface to receive vapor therefrom, a saturated vapor outlet conduit in communication with the vapor space of the drum to receive saturated vapor therefrom, burner control means responsive to pressure in said drum and operatively associated with said burner means, said burner control means being operative by said pressure in the drum so as to increase the firing rate of fuel to said burners when the pressure in the drum decreases below a predetermined value and to decrease the tiring rate of fuel to said burners when the pressure in the drum increases above a predetermined value, a heat exchanger, duid conduit means communicating with said heat exchanger and through which heated fluid is conducted to the heat exchanger, feed liquid conduit means communicating wtih the heat exchanger and through which feed liquid to be heated is conducted to the heat exchanger, the heat exchanger being so constructed and arranged that said heated fluid and feed liquid pass in indirect heat exchange relationship with one another, said feed liquid thereby becoming heated and said fluid becoming cool, feed liquid control means located to control the How of feed liquid to said heat exchanger, the feed liquid control means being operative to increase or decrease the ow of feed liquid to said heat exchanger, said feed liquid control means being operative in response to the change of liquid level in said drum so as to decrease the ow of feed liquid to the drum when the liquid level in the drum exceeds a predetermined level and to increase the dow of feed liquid to the drum when the liquid level in the drum falls below said predetermined level,

'6 a lcooled hind outlet conduit in rcommunication with the vheat exchanger to receive cooled fluid therefrom and withssaid huid flow path inlet to deliver cooled duid thereto, a :heated Lfeed :liquid conduit iin communication with kthe lheat exchanger to `receive heated feed Iliquid therefrom and with "said vapor and liquid Idrum to deliver heated .feed liquid thereto, a 'bypass conduit `communicating with Isaid fluid `conduit and fsaid fluid ow path so that ud from said iluid conduit may be bypassed -around said heat exchanger and irrto said Vfluid flow path, and temperature responsive fcontrol means operatively associated with said bypass to control the 4ow of fluid through 'said bypass, vsaid temperature responsive control means ybeing 'operative in response to Isaid temperature to increase or decrease `the ow 4of huid through said bypass, the temperature control means being. responsive to the temperatures of .said heated uid fso as to increase the ow -of Iiluid through the bypass 'and around the heat lexchanger when the temperature of the heated iluid decreases below a predetermined temperature and to decrease the ow of fluid through the bypass so as to increase the flow thereof through the heat exchanger when the temperature 'of -said heated uid increases above a predetermined temperature.

3. Vapor generating and uid heating :apparatus cornprising a :setting having a furnace therein, burner means for producing a stream of products of combustion in 'the furnace, oil conducting tubular members in the setting forming an oil .flow path for oil to be heated, said flow path having an inlet for oil to be heated and an loutlet .for heated oil, said oil conducting tubular members being disposed in 4the setting in heat exchange lrelationship with said stream of products of combustion, vapor generating surface so positioned in the furnace that said products of combustion ow in heat exchange relationship therewith prior to flowing in heat exchange relationship with said oil conducting tubular members, said vapor generating surface having a water inlet through which water is fed thereto and a vapor 4outlet through which a mixture -olf Water and vapor flows therefrom, a vapor and water drum with a vapor space and a water space therein, the water Space being in communication with the vapor generating surface inlet so that water is delivered thereto from the drum, the vapor space being in communication with the vapor outlet of the vapor generating surface to receive vapor therefrom, a saturated vapor outlet conduit in communication with the vapor space of the drum to receive saturated vapor therefrom, burner control means responsive to pressure in said drum and operatively 'associated with said burner means, said burner control means being operative by said pressure in the drum so as. to ncrease the tiring rate of fuel to said burners when the pressure in the drum decreases and to decrease the firing rate vof fuel to said burners' when the pressure in the drum increases, a heat exchanger, oil conduit means cornmunicating with said heat exchanger and through which heated oil is conducted to the heat exchanger, feed water conduit means communicating with the heat exchanger and through which feed water to be heated is conducted to the heat exchanger, the heat exchanger being so constructed and arranged that said heated oil and feed water pass in indirect heat exchange relationship with one another, said feed water thereby becoming heated and said oil becoming cooled, feed 'water control means located to control the ow of feed water to said heat exchanger, the feed water control means being operative to increase or decrease the flow of feed water to said heat exchanger, said feed water control means being operative in response to the change of water level in said drum vso as' to decrease the ow of feed water to the drum when Vthe water level in the drum exceeds a predetermined level and to increase the flow of feed water to the drum 'when the water level in the drum falls below said predetermined level, a cooled oil outlet conduit in communication with the heat exchanger to receive cooled oil therefrom and with said oil flow path inlet to deliver cooled oil thereto, a. heated feed water conduit in communication with the heat exchanger to receive heated feed water therefrom and with said vapor and liquid drum to deliver heated feed water thereto, a bypass conduit communicating withV said oil conduit and said oil flow path so that oil from said oil conduit may be bypassed around said heat exchanger and into said oil ow path, and temperature responsive control means operatively associated with said bypass to control the ow of oil through said bypass', said temperature responsive control means being operative in response heated oil decreases and to decrease the flow of oil through the bypass so as to increase the flow thereof through the heat exchanger when the temperature of said heated oil increases.

4. Apparatus for heating fluids comprising walls forming a furnace, burner means for producing a stream of products of combustion in the furnace, fluid conducting tubular members adjacent a wall of the furnace, said tubular members forming a fluid flow path for fluid to be heated, said flow path having an inlet for fluid to be heated and an outlet for heated fluid, said fluid heating tubular members being in radiant heat exchange relationship with said stream of products of combustion, vapor generating tubes positioned in the furnace adjacent said fluid heating tubular members on the furnace side thereof so that said products of combustion flow in radiant heat exchange relationship therewith prior to flowing in radiant heat exchange relationship with said fluid conducting tubular members, said vapor generating f tubes being connected in series which series has a liquid inlet through which liquid is fed thereto and a vapor outlet through which a mixture of liquid and vapor flows therefrom, a vapor and liquid drum with a vapor space and a liquid space therein, the liquid space being in communication with said liquid inlet so that liquid is delivered thereto from the drum, the vapor space being in cornmunication with said vapor outlet, a saturated vapor outlet conduit in communication with the vapor space of the drum to receive saturated vapor therefrom, burner control means responsive to pressure in said drum and operatively associated with said burner means, said burner control means being operative by said pressure in the drum so as to increase the firing rate of fuel to said burners when the pressure in the drum decreases and to decrease the firing rate of fuel to said burners when the pressure in the drum increases, a heat exchanger, fluid conduit means communicating with said heat exchanger and through which heated fluid is conducted to the heat exchanger, feed liquid conduit means communicating with the heat exchanger and through which feed liquid to be heated is conducted to the heat exchanger, the heat exchanger being so constructed and arranged that said heated fluid and feed liquid pass in indirect heat exchange relationship with one another, said feed liquid thereby becoming heated and said fluid becoming cooled, feed liquid control means located to control the flow of feed liquid to said heat exchanger, the feed liquid control means being operative to increase or decrease the flow of feed liquid to said heat exchanger, said feed liquid control means being operative in response to the change of liquid level in said drum so as to decrease the flow of feed liquid to the drum when the liquid level in the drum exceeds a predetermined level and to increase the flow of feed liquid to the drum when the liquid level in the drum falls below said predetermined level, a cooled fluid outlet conduit in communication with the heat exchanger to receive cooled fluid therefrom and with said fluid flow path inlet to deliver cooled fluid thereto, a heated feed liquid conduit in communication with the heat exchanger to receive heated feed liquid therefrom and with said vapor and liquid drum to deliver heated feed liquid thereto, a bypass conduit communicating with said fluid conduit and said fluid flow path so that fluid from said fluid conduit may be bypassed around said heat exchanger and into said fluid flow path, and temper- -to increase the flow thereof through the heat exchanger when the temperature of said heated fluid increases.

5. The apparatus dened in claim 4 wherein the fluid conducting tubular members extend in a horizontal plane sin, verticallyspaced `relationship to one another and int ,l 8 spaced relationship to the furnace wall, said fluid conducting tubular members extending along the wall being serially connected, and wherein the vapor generating tubes extend in a horizontal plane 'in vertically spaced relationship to one another and adjacent to and horizontally spaced from the fluid conducting tubular members on the furnace side thereof, said vapor generating tubes along each wall being serially connected and so arranged in relationship to the fluid conducting tubular members that the vapor generating tubes are horizontally opposite the spaces between vertically spaced tubular members.

6. Apparatus for heating fluids comprising walls forming a furnace, each side wall having a vertically extending portion and a vertically and inwardly inclined portion above the vertically extending portion and connecting with the roof of the furnace, fluid conducting tubular members adjacent the side walls of the furnace, spaced banks of tubular members at the bottom of the furnace spaced from the side walls, each bank of tubular members being connected with the tubular members adjacent the side wall adjoining the bank to provide separate paths of flow of the fluid to be heated through the heater, said paths of flow having an inlet for fluid to be heated and an outlet for heated fluid, a baffle above said banks of tubular members having terminal portions spaced from the side walls of the furnace to provide a passage in the furnace adjacent each side wall thereof, a plurality of burners in an end wall of the furnace to produce streams of products of combustion in the furnace, the space between said banks of tubular members being in communication with a furnace outlet and providing a gas outlet passage for the gases flowing from the furnace and over said banks of tubular members, vapor generating tubes positioned in the furnace adjacent said fluid heating tubular members adjacent the side walls of the furnace, said vapor generating tubes being positioned on the furnace side of the fluid heating members so that said products of combustion flow in radiant heat exchange relationship therewith prior to flowing in radiant heat exchange relationship with said fluid conducting tubular members, said vapor generating tubes being connected in series which series has a liquid inlet through which liquid is fed thereto and a vapor outlet through which a mixture of liquid and vapor flows therefrom, a vapor and liquid drum with a vapor space and a liquid space therein` the liquid space being in communication with said liquid inlet so that liquid is delivered thereto from the drum, the vapor space being in communication with said vapor outlet. a saturated vapor outlet conduit in communication with the vapor space of the drum to receive saturated vapor therefrom, burner control means responsive to pressure in said drum and operatively associated with said burner means, said burner control means being operative by said pressure in the drum so as to increase the firing rate of fuel to said burners when the pressure in the drum decreases and to decrease the firing rate of fuel to said burners when the pressure in the drum increases, a heat exchanger, fluid conduit means communicating with said heat exchanger and through which heated fluid is conducted to the heat exchanger, feed liquid conduit means communicatina with the heat exchanger and through which feed liquid to be heated is conductedto the heat exchanger, the heat exchanger being so constructed and arranged that said heated fluid and feed liquid pass in indirect heat exchange relationship with one another, said feed liquid thereby becoming heated and said fluid becoming cooled, feed liquid control means located to control the flow of feed liquid to said heat exchanger, the feed liquid control means being operative to increase or decrease the flow of feed liquid to said heat exchanger, said feed liquid control means being operative in response to the change of liquid level in said drum so as to decrease the flow of feed liquid to the drum when the liquid level in the drum exceeds a predetermined level and to increase the flow of feed liquid to the drum when the liquid level in the drum falls below said predetermined level, a cooled fluid outlet conduit in communication with the heat exchanger to receive cooled fluid therefrom and with said fluid flow path inlet to deliver cooled fluid thereto, a heated feed liquid conduit in communication with the heat exchanger to receive heated feed liquid therefrom and with said vapor and liquid drum to deliver heated feed liquid thereto, a bypass conduit communicating with said fluid conduit and said fluid flow path so that .fluid from said fluid conduit maybe bypassed around said heat exchanger and into said fluid flow path, and ternperature responsive control means operatively associated with said bypass to control the flow of fluid through said bypass, said temperature responsive control means being operative in response to said temperature to increase or decrease the flow of fluid through said bypass, the temperature control means being responsive to the temperatures of said heated fluid so as to increase the ow of fluid through the bypass and around the heat exchanger when the temperature of the heated fluid decreases and to decrease the flow of uid through the bypass so as to increase the flow thereof through the heat exchanger when the temperature of said heated fluid increases.

7. The apparatus defined in claim 6 wherein the fluid conducting tubular members extend in a horizontal plane in vertically spaced relationship to one another and in spaced relationship to the furnace wall, and uid conducting tubular members extending along each wall being serially connected, and wherein the vapor generating tubes extend in a horizontal plane in vertically spaced relationship to one another and adjacent to and horizontally spaced from the uid conducting tubular members along each wall and on the furnace side thereof, and vapor generating tubes along each wall being serially connected and so arranged in relationship to the fluid conducting tubular members that the vapor generating tubes are horizontally opposite the spaces between vertically spaced tubular members.

8. Vapor generating and uid heating apparatus comprising a setting having a furnace therein, burner means for producing a stream of products of combustion in the furnace, fluid conducting tubular members in the setting forming a fluid flow path for fluid to be heated, said ow path having an inlet for fluid to be heated and an outlet for heated fluid, said fluid conducting tubular members being disposed in the setting in heat exchange relationship with said stream of products of combustion, vapor generating surface so positioned in the furnace that said products of combustion flow in heat exchange relationship therewith prior to flowing in heat exchange relationship with said fluid conducting tubular members, said vapor generating surface having a liquid inlet through which liquid is fed thereto and a vapor outlet through which a mixture of liquid and vapor ilows therefrom, a vapor and liquid drum with a vapor space and a liquid space therein, the liquid space being in communication with the vapor generating surface inlet so that liquid is delivered thereto from the drum, the Vapor space being in communication with the vapor outlet of the vapor generating surface to receive vapor therefrom, a saturated vapor outlet conduit in communication with the vapor space of the drum to receive saturated vapor therefrom, a burner valve operatively associated with said burner means, pressure responsive means operatively associated with said burner valve and responsive by pressure in the drum so as to increase the ring rate of fuel to said burners when the pressure in the drum decreases and to decrease the firing rate of fuel to said burners when the pressure in the drum increases, a heat exchanger, uid conduit means communicating with said heat exchanger and through which heated iluid is conducted to the heat exchanger, feed liquid conduit means communicating with the heat exchanger and through which feed liquid to be heated is conducted to the heat exchanger, the heat exchanger being so constructed and arranged that said heated uid and feed liquid pass in indirect heat exchange relationship with one another, said feed liquid thereby becoming heated and said iluid becoming cooled, a feed valve located to control the ow of feed liquid to said heat exchanger, liquid level responsive means operatively associated with said feed valve and responsive to the change of liquid level in said drum so as to decrease the ow of feed liquid to the drum when the liquid level in the drum exceeds a predetermined level and to increase the flow of feed liquid to the drum when the liquid level in the drum falls below said predetermined level, a cooled iluid outlet conduit in communication with the heat exchanger to receive cooled uid therefrom and with said fluid iiow path inlet to deliver cooled fluid thereto, a heated feed liquid conduit in communication with the heat exchanger to receive heated feed liquid therefrom and with said vapor and liquid drum to deliver heated feed liquid thereto, a bypass conduit communicating with said uid conduit and said fluid ow path so that uid from said lluid conduit may be bypassed around said heat exchanger and into said fluid ow path, and a iluid valve operatively associated with said bypass to control the ow of uid through said bypass, temperature responsive means operatively associated with said uid valve and responsive to the temperatures of said heated fluid so as to increase the ow of fluid through the bypass and around the heat exchanger when the temperature of the heated uid decreases and to decrease the flow of fluid through the bypass so as to increase the ow thereof through the heat exchanger when the temperature of said heated fluid increases. 

1. VAPOR GENERATING AND FLUID HEATING APPARATUS COMPRISING A SETTING HAVING A FURNACE THEREIN, BURNER MEANS FOR PRODUCING A STREAM OF PRODUCTS OF COMBUSTION IN THE FURNACE, FLUID CONDUCTING TUBULAR MEMBERS IN THE SETTING FORMING A FLUID FLOW PATH FOR FLUID TO BE HEATED, SAID FLOW PATH HAVING AN INLET FOR FLUID TO BE HEATED, AND AN OUTLET FOR HEATED FLUID, SAID FLUID TO BE HEATED AND AN OUTLET BEING DISPOSED IN THE SETTING IN HEAT EXCHANGE, RELATIONSHIP WITH SAID STREAM OF PRODUCTS OF COMBUSTION, VAPOR GENERATING SURFACE SO POSITIONED IN THE FURNACE THAT SAID PRODUCTS OF COMBUSTION FLOW IN HEAT EXCHANGE RELATIONSHIP THEREWITH PRIOR TO FLOWING IN HEAT EXCHANGE RELATIONSHIP WITH SAID FLUID CONDUCTING TUBULAR MEMBERS, SAID VAPOR GENERATING SURFACE HAVING A LIQUID INLET THROUGH WHICH LIQUID IS FED THERETO AND A VAPOR OUTLET THROUGH WHICH A MIXTURE OF LIQUID AND VAPOR FLOWS THEREFROM, A VAPOR AND LIQUID DRUM WITH A VAPOR SPACE AND A LIQUID SPACE THEREIN, THE LIQUID SPACE BEING IN COMMUNICATION WITH THE VAPOR GENERATING SURFACE INLET SO THAT LIQUID IS DELIVERED THERETO FROM THE DRUM, THE VAPOR SPACE BEING IN COMMUNICATION WITH THE VAPOR OUTLET OF THE VAPOR GENERATING SURFACE TO RECEIVE VAPOR THEREFROM, A SATURATED VAPOR OUTLET CONDUIT IN COMMUNICATION WITH THE VAPOR SPACE OF THE DRUM TO RECEIVE SATURATED VAPOR THEREFROM, BURNER CONTROL MEANS RESPONSIVE TO PRESSURE IN SAID DRUM AND OPERATIVELY ASSOCIATED WITH SAID BURNER MEANS, SAID BURNER CONTROL MEANS BEING OPERATIVE BY SAID PRESSURE IN THE DRUM SO AS TO INCREASE THE FIRING RATE OF FUEL TO SAID BURNERS WHEN THE PRESSURE IN THE DRUM DECREASES AND TO DECREASE THE FIRING RATE OF FUEL TO SAID BURNERS WHEN THE PRESSURE IN THE DRUM INCREASES, A HEAT EXCHANGER, FLUID CONDUIT MEANS COMMUNICATING WITH SAID HEAT EXCHANGER AND THROUGH WHICH HEATED FLUID IS CONDUCTED TO THE HEAT EXCHANGER, FEED LIQUID CONDUIT MEANS COMMUNICATING WITH THE HEAT EXCHANGER AND THROUGH WHICH FEED LIQUID TO BE HEATED IS CONDUCTED TO THE HEAT EXCHANGER, THE HEAT EXCHANGER BEING SO CONSTRUCTED AND ARRANGE THAT 